Yes — Illinois code 77 Ill. Adm. Code 820.340 requires an accessible telephone with posted emergency numbers.
Illinois requires the pool telephone to be accessible, with emergency numbers posted at or near the phone.
Citation: 77 Ill. Adm. Code 820.340
Posting the numbers is not optional here — inspectors commonly check for a visible sign with 911 and the pool's address next to the phone, since dispatchers need the address to send help quickly.
SouthEast Telephone installs and monitors cellular emergency pool phones nationwide and can help you meet Illinois's requirements.